The present disclosure is directed to a process for treating steel alloys, such as PYROWEAR® alloys, used for components, such as gears.
In the design and manufacture of steel components, there is often a need to modify properties of the material. It is well recognized that carburizing is a process suited for hardening the surface and sub-surface of the steel component. Carburizing can be broadly considered as either an atmospheric carburization process or a vacuum carburization process. In the vacuum carburization process, the component is heated to an elevated temperature within a carburizing furnace, and a carburizing gas is introduced into the environment so that carbon atoms are diffused into the surface and sub-surface of the steel material. The carbon content in the surface and near sub-surface of the component is increased while the carbon content within the core of the component remains unaltered. The characteristics of the component have this been modified to provide a hardened outer surface surrounding an interior core.
It has been suggested that, when using a stainless steel, such as PYROWEAR® 675, one should first oxidize the surface of the component prior to exposure to the carburizing environment. In such a process, the component is grit blasted and placed in an air furnace at a temperature of 1300 degrees Fahrenheit for about one hour to form an oxide on its surface. Upon the component being subjected to the carburizing environment, the oxidized surface facilitates the absorption of carbon by the material.
In a carburizing process, the time and temperature that the material is subjected to while in the carburizing environment will determine the surface hardness, case depth, hardness profile, and carbide microstructure of the hardened portion of the material.
Gears made from steel alloys need to have the proper hardness of the gear teeth without through hardening of the tips of the gear teeth.